Add external references to object factory

stix2/environment.py

@@ -1,10 +1,12 @@
 
 class ObjectFactory(object):
 
-    def __init__(self, created_by=None, object_markings=None, granular_markings=None):
+    def __init__(self, created_by=None, object_markings=None,
+                 granular_markings=None, external_references=None):
         self.created_by = created_by
         self.object_markings = object_markings
         self.granular_markings = granular_markings
+        self.external_references = external_references
 
     def create(self, cls, **kwargs):
         if self.created_by is not None:
@@ -13,5 +15,7 @@ class ObjectFactory(object):
             kwargs['object_marking_refs'] = self.object_markings
         if self.granular_markings is not None:
             kwargs['granular_markings'] = self.granular_markings
+        if self.external_references is not None:
+            kwargs['external_references'] = self.external_references
 
         return cls(**kwargs)

stix2/test/test_environment.py

@@ -37,3 +37,12 @@ def test_object_factory_granular_markings():
                                   granular_markings=marking)
     ind = factory.create(stix2.Indicator, **INDICATOR_KWARGS)
     assert "created_by_ref" in ind.granular_markings[0].selectors
+
+
+def test_object_factory_external_resource():
+    ext_ref = stix2.ExternalReference(source_name="ACME Threat Intel",
+                                      description="Threat report")
+    factory = stix2.ObjectFactory(external_references=ext_ref)
+    ind = factory.create(stix2.Indicator, **INDICATOR_KWARGS)
+    assert ind.external_references[0].source_name == "ACME Threat Intel"
+    assert ind.external_references[0].description == "Threat report"